Thread: Sample Semaphore program on linux

Dear All,

I am looking for a Sample Semaphore program on linux, Plz help me

Originally Posted by ashok449

Dear All,

I am looking for a Sample Semaphore program on linux, Plz help me

GIFY.

I have an Idea on Semaphores but dont know how to apply on a real time application.

is this semaphore signalling? thats a cool little programming idea for a laugh, morse code translator would be good too..

Ok, here is some code I found on net. Plz tell me how this works.

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

#define KEY (1492)
void main()
{
   int id;  
   struct sembuf operations[1];
   
   int retval; 

   
   id = semget(KEY, 1, 0666);
   if(id < 0)
  
   {
      fprintf(stderr, "Program sema cannot find semaphore, exiting.\n");
      exit(0);
   }

   /* Do a semaphore V-operation. */
   printf("Program sema about to do a V-operation. \n");

   
    operations[0].sem_num = 0;
    /* Which operation? Add 1 to semaphore value : */
    operations[0].sem_op = 1;
    /* Set the flag so we will wait : */   
    operations[0].sem_flg = 0;


    /* So do the operation! */
    retval = semop(id, operations, 1);

    if(retval == 0)
    {
       printf("Successful V-operation by program sema.\n");
    }
    else
    {
       printf("sema: V-operation did not succeed.\n");
	perror("REASON");
    }
}

thanks in advance ...

retval = semop(id, operations, 1);


if retval ==0 then semop is successfull which means I need to place my code here, If so how to aquire/release again.

Code:

if(retval ===0)
{
  // semop success
do some stuff .....
// how to release or aquire lock 

operations[0].sem_num = 0;
    /* Which operation? Add 1 to semaphore value : */
    operations[0].sem_op = -1;
    /* Set the flag so we will wait : */   
    operations[0].sem_flg = 0;

semop(id, operations, 1); //  is this corrrect

}

if retval ==0 then semop is successfull which means I need to place my code here, If so how to aquire/release again.

Now, Anyone can give me a small real-time example on semaphore

zacs7 and brewbuck, you see in this thread I almost provide everything except a clarification which I require. Thats all I need and thats all about a forum is.


If getting sample code from google is enough then what is the requirement of a forum.

Forum means expressing yourself and getting advices.


Anyhow thanks for everything...